Various types of light modulators are known. These include, for example, Mach-Zehnder type modulators and electroabsorption modulators. The following literature references describe various Mach-Zehnder type modulators;
High-Speed Electrooptic Modulation in GaAs/GaAlAs Waveguide Devices, by Robert G. Walker, Journal of Lightwave Technology, Vol LT-5, No. 10, pp 1444-1453, October, 1987 and the references therein;
Broadband Y-branch electro-optic GaAs waveguide inter-ferometer for 1.3 micrometers, by P. Buchmann et al, Applied Physics Letters, Vol 46, No. 5, pp 462-464 (1985);
Broad-Band Guided-Wave Electrooptic Modulators, by Richard A. Becker, The Journal of Quantum Electronics, Vol. QE-20, No. 7, July, 1984, pp 723-727;
The following product publications describe what is believed to be the state Mach-Zehnder optical modulators:
LC1000 Series GaAs Optical Modulators for D.C. to 50 GHz, GEC-Marconi, Materials Technology, Caswell Towcester, Northamptonshire, U.K.
2.5 GHz, 8 & 18 GHz Integrated Optical Amplitude Modulators, GEC Advanced Optical Products, West Hanningfield Road, Great Baddow, Chelmsford, Essex, U.K.
The following reference shows an optical switch which employs a multimode interference coupler:
Novel 1×N and N×N integrated optical switches using self-imaging multimode GaAs/AlGaAs waveguides by R. M. Jenkins et al., Applied Physics Letters, Vol 64 (6), 7 Feb. 1994, pp. 684-686.